In the field of orthopedic surgery, and particularly spinal surgery, it is well known to correct an injury, malformation, or other defect by use of an implanted rod affixed to the body part to be corrected. For example, rod systems have been developed for correcting the positioning of and stabilizing the spine, and for facilitating fusion at various levels of the spine. In one such system, the rod is disposed longitudinally along a length of the spine. The rod is preferably bent, either prior to or during surgery, to correspond to the normal curvature of the spine in the particular region being instrumented, or to such other curvature as the surgeon may deem appropriate to correct the defect. For example, the rod can be bent to form a normal kyphotic curvature for the thoracic region of the spine, or to form a normal lordotic curvature for the lumbar region. The rod is engaged to a number of fixation elements fixed to or engaged with the vertebrae along the segment of the spinal column.
A variety of fixation elements can be provided that are configured to engage the vertebrae. For instance, one such fixation element is a laminar hook, configured to engage a lamina of the vertebra. Another prevalent fixation element is a spinal screw which can be threaded into a pedicle or other portion of vertebral bone. Examples of such spinal screws are seen in U.S. Pat. No. 5,005,562 to Cotrel, the disclosure of which is incorporated herein by reference. An alternative type of fixation element is a multi-axial bone screw, such as that as disclosed in U.S. Pat. Nos. 5,797,911 and 5,879,350 to Sherman et al., each of which is also incorporated herein by reference in its entirety. Further types of bone screws, hooks, bolts, or other fixation elements are known in the art.
In one typical spinal procedure, an elongated implant (e.g. a rod) is coupled to two or more fixation elements (e.g. bone screws) that are fixed to opposite sides of the spine or spinous processes. The bone screws are first threaded into a portion of several vertebral bodies, such as the pedicles of these vertebrae. The rod is coupled to the bone screws to provide corrective and stabilizing forces to the spine. Affixing a rod to a bone screw generally requires the rod to be in close adjacent position or in contact with the screw. For example, with respect to bone screws as disclosed in the Cotrel '562 patent and the Sherman '911 and '350 patents identified above, a rod and an implanted screw must be moved with respect to each other so that the rod occupies space within a channel or other opening in the screw. The rod is then coupled to the implanted bone screw using a set screw, plug or other appropriate fastener. The process of placing a rod within or adjacent to an implanted fixation element so that they can be coupled together is termed “reducing” the rod.
Rod reduction is commonly performed by a surgeon using his or her hands and/or rigid tools as pliers, levers or other instrumentation adaptable to create the necessary pushing and/or pulling forces on the implanted screw and rod. Such procedures generally require the surgeon to place the rod directly over the implanted fixation element, intersecting a longitudinal axis of the fixation element. Consequently, access to the rod and the implanted fixation element along that axis, i.e. directly above the opening in the fixation element into which the rod is to be placed, is necessary or at least highly desirable. However, such access can be difficult depending on such factors as the malformation to be corrected and the overall physiology of the patient, and can be very difficult in procedures in which surgical invasiveness is to be minimized, as a result of the small ports or incisions of such procedures. Additionally, with use of mono-axial screws, the physiology of the patient can require that the screw be placed at an angle such that the surgeon would have difficulty accessing and exerting force in the necessary orientation on the rod and/or fixation element. With multi-axial fixation devices, the orientation of an unsecured rod-receiving part of the fixation element can be even more varied with respect to the rod and/or the surgeon. Consequently, the surgeon is still frequently faced with the task of reducing a rod from an awkward angle.
Various attempts in the prior art have been made in providing rod reducing instruments, such as described in U.S. Pat. No. 6,036,692 to Burel et al.; U.S. Pat. No. 5,910,141 to Morrison et al.; and U.S. Pat. No. 5,720,751 to Jackson; each of which is incorporated herein by reference in its entirety. However, needs remain in the industry for rod reducing instruments that can be used efficiently, safely and securely in rod reduction procedures and for rod reduction instruments that can be used in both minimally invasive and open surgical approaches to the site of rod attachment.